Narrow Headed Ant (Formica exsecta) or Excised Wood Ant is a species of ant native to the British Isles.

A rare formicine ant with a deeply excised head, F. exsecta forms small mounds up to around a foot in height consisting of much finer material than that used by "true" wood ants of the F. rufa group.

F. exsecta is placed in the Formica exsecta group within the genus and is closely related to Formica exsectoides, an American species whose colonies form vast networks.

In Britain, F. exsecta can be found only in a few scattered heathland locations in the South West - principally Chudleigh Knighton heath and nearby Bovey heath, and in the central Scottish Highlands (including Rannoch Moor). A population center previously existed in the New Forest, and such eminent myrmecologists as Horace Donisthorpe recorded this species there and in Parkhurst forest on the Isle of Wight in the last century, but this seems to have declined considerably over the past few decades, and recent searches in such locations have failed to find any trace of colonies.

Also see:

• British ants
• List of ant genera (alphabetical)
• List of locales in Britain where ant species have become locally extinct